@krewe/x402-client

Pay-per-call client for the krewe decentralized inference network on Base. Settles each call in USDC via EIP-3009 transferWithAuthorization — no API keys, no signup, no rate-limit dashboards. If your wallet has USDC on Base, you can call the network.

The network runs 3-of-3 fan-out with 2-of-3 byte-equal consensus on every job — your inference call is independently verified before you get a response. See krewe-AI/krewe for the full protocol.

Install

pnpm add @krewe/x402-client viem
# or: npm i @krewe/x402-client viem

Quickstart

import { createX402Client } from "@krewe/x402-client";
import { privateKeyToAccount } from "viem/accounts";

const client = createX402Client({
  signer: privateKeyToAccount(process.env.AGENT_PRIVATE_KEY as `0x${string}`),
});

const result = await client.predict({
  kind: "text.structure",
  payload: {
    text: "Email [email protected] about the meeting on 2026-06-12.",
  },
});

console.log(result.output);
// → { emails: ["[email protected]"], urls: [], dates: ["2026-06-12"], numbers: [] }
console.log(`Paid: ${result.paymentTxHash} (replicas=${result.replicas})`);

Supported job kinds

| kind | Price (USDC) | Description | |-------------------|--------------|------------------------------------------------------| | text.structure | $0.005 | Extract emails, URLs, dates, numbers, phones | | text.embed | $0.010 | Sentence embeddings (Xenova/all-MiniLM-L6-v2) | | web.scrape | $0.020 | Fetch + clean a small URL payload | | text.complete | $0.050 | Quantized SLM completion (Xenova/Qwen2.5-0.5B) |

How it works

1. client.predict(req) POSTs /v2/predict without payment → orchestrator returns HTTP 402 with an x402 challenge (recipient, USDC amount, nonce, 5-minute deadline).
2. SDK signs the challenge as an EIP-3009 TransferWithAuthorization typed-data message using your wallet.
3. SDK re-POSTs with X-PAYMENT: base64(json({challenge, from, v, r, s})).
4. Orchestrator verifies the signature off-chain, submits transferWithAuthorization on-chain, runs the inference job across 3 miners, returns the consensus result with the on-chain paymentTxHash.

The orchestrator pays the gas (~$0.001 on Base) and recovers it from the payment itself.

Advanced: two-step flow

If you want to show a user the price before signing:

const challenge = await client.getChallenge({ kind: "text.complete", payload: { prompt: "…" } });
console.log(challenge.description); // "$0.050000 for text.complete"

// (display to user, get confirmation, …)

const payment = await client.signChallenge(challenge);
const result  = await client.submitWithPayment({ kind: "text.complete", payload: {...} }, payment);

Spending cap

By default the SDK rejects any quoted price > $0.10 per call. Override with maxPricePerCallUsdc:

const client = createX402Client({
  signer,
  maxPricePerCallUsdc: 1_000_000n, // $1.00 per call
});

Browser usage

The SDK uses fetch and Buffer only — works in Node ≥ 18, Bun, Deno, Cloudflare Workers, Vercel Edge, and browsers (with a wallet-injected signer like wagmi's useWalletClient).

import { createWalletClient, custom } from "viem";
import { base } from "viem/chains";

const wallet = createWalletClient({ chain: base, transport: custom(window.ethereum) });
const [address] = await wallet.getAddresses();

const client = createX402Client({
  signer: {
    address,
    signTypedData: (params) => wallet.signTypedData({ account: address, ...params }),
  },
});

License

MIT. See LICENSE.